<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html,
        body {
            width: 100%;
            margin: 0px;
        }
        h1{
            height: 100px;
            margin: 20px 0 0;
        }
        #left,
        #right {
            width: 200px;
            height: 200px;
            background-color: hotpink;
            top: 120px;
            position: absolute;
        }

        #left {
            left: 0px;
        }

        #right {
            right: 0px
        }
        #center{
            margin: 2px 210px;
           height: 200px;
           background-color: rgb(163, 105, 255);
        }
    </style>
</head>

<body>
    <h1>宽度自适应，两边固定200px</h1>
    <div id="left">左边</div>
    <div id="center">中间</div>
    <div id="right">右边</div>

</body>

</html>